It is HIGHLY unusual then. Perhaps you are the only one to be able to do it. Even in medical literature they say you can't.
[link to www.webmd.com]
[link to en.wikipedia.org]
[link to healthyliving.msn.com]
[link to www.nhs.uk]
etc, etc, etc

I have NEVER been able to, despite many, many episodes of it. My brother has never been able to. My cousin, my nephew. All of them have said the same thing. Cannot talk during sleep paralysis.